创建具有多个可变条件的新数据框并提取失败的原因 - pandas

Question

我有下面的代码。考虑到以下限制，我想创建如下输出：A > 5，B > 4，C > 3如果不满足条件，我想读取数据框中的下面一行，存储数据，并创建一个名为“失败原因”的新列，其中列出 A、B 或 C 是否失败。然后我希望脚本也报告通过的数据帧的行的“X”、“Y”和“Z”的相应值。此后，脚本应按“组”分组并显示每组的最大“Hs”。我真的很难在数据框中使用多个变量来完成这项工作...任何帮助将不胜感激所需输出   Group   Hs Fail Reason    X    Y     Z0      1  1.0      [A, B]  0.9  1.9  0.541      2  0.5   [A, B, C]  0.8  2.7  0.43主要代码- 我当前的尝试import pandas as pddata = [[1,0.5,8,8,8,0.85,1.64,0.5],        [1,1,8,8,8,0.9,1.9,0.54],        [1,1.5,0,0,10,1.1,2.0,0.74],        [2,0.5,6,5,4,0.8,2.7,0.43],        [2,1,1,1,1,0.9,2.9,0.45],        [2,1.5,1,2,1,1.1,3.1,0.47]]columns = ['Group', 'Hs', 'A', 'B', 'C', 'X', 'Y', 'Z']df = pd.DataFrame(data=data, columns=columns)Limit_A = 5Limit_B = 4Limit_C = 3# Opens an empty dataframe for appendingdf_new = pd.DataFrame(columns=['Group', 'Hs'])groups = df['Group'].unique()# for g in groupsfor g in groups:    # Create new temp dataframe    df_1 = df[df['Group'] == g]    # Input conditions, checks the columns one by one are NOT EQUAL TO ZERO. Outputs boolean values.    pass_criteria = (df_1['A'] > Limit_A) & (df_1['B'] > Limit_B) & (df_1['C'] > Limit_C)    # PASSES DATAFRAME. Locates rows where the conditions of mask_1 are SATISFIED and creates another temp dataframe.    df_passes = df_1.loc[pass_criteria]    # Find the max value in the dataframe e.g. the greatest operational wave height    max_num = df_passes['Hs'].max()    # Does the opposite of mask_1    fail_criteria = (df_1['A'] < Limit_A) & (df_1['B'] < Limit_B) &(df_1['C'] < Limit_C)    # FAILED DATAFRAME. Locates rows where the conditions of pass_criteria are SATISFIED and creates another temp dataframe.    df_fails = df_1.loc[fail_criteria]    # Uses the dataframe with FAIL and mkes the value_vars rows in the melted dataframe    melted = pd.melt(df_fails, value_vars=['A', 'B', 'C'])print(df_new)

Answer 1

IIUC 首先将 A、B、C 列与您的限制进行比较，然后agg返回map结果：

res = df[["A","B","C"]]>[5,4,3]

s = (pd.concat([df, (~res[~res.all(1)]).agg(lambda x: res.columns[x].tolist(),

                                              axis=1).rename("Fail reason")], axis=1)

       .dropna().drop_duplicates("Group").set_index("Group")["Fail reason"])

print (df.assign(failed_reason=df["Group"].map(s))

         .loc[res.all(1)].sort_values(["Group", "Hs"])

         .drop_duplicates("Group", keep="last"))

   Group   Hs  A  B  C    X    Y     Z failed_reason

1      1  1.0  8  8  8  0.9  1.9  0.54        [A, B]

3      2  0.5  6  5  4  0.8  2.7  0.43     [A, B, C]